“This is clearly a major issue for the intelligence community,” Coats told a group of journalists at his office complex in suburban Virginia. “It’s one of our top priorities.”

The administration of President Donald Trump has called on Congress to renew and make permanent some powers under the Foreign Intelligence Surveillance Act, which expire at the end of this year. Those powers permit collection of electronic communications of foreigners who are deemed potential threats to U.S. national security, a list of targets that this year topped 106,000.

A scattering of legislators from both parties have called for limitations on surveillance power, voicing concerns from libertarian and civil liberties perspectives that U.S. citizens are getting swept up in the data collection.

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“There’s just been some stuff floating around that, let me be kind, just misinterprets what 702 does,” Coats said, referring to Section 702 of the surveillance act that contains the key legal authorities.

Senior U.S. government officials from Coats’ office, the CIA, the National Security Agency, the FBI and the Department of Justice answered questions from journalists during an hourlong meeting about aspects of the surveillance, and they offered details of several cases in which surveillance helped thwart terrorist attacks or operations against the United States.

One of the cases was of Shawn Joel Parson, a Trinidad native who traveled to Syria in 2014 and joined in a cyber unit of the Islamic State, working under the wing of British-born Junaid Hussain, a prolific hacker.

Parson posted personal information about U.S. military personnel to social media in an effort to have radicals target them for attack. Through electronic targeting, U.S. officials took action that led to Parson’s killing in 2015, officials said.

Officials voiced concern that restricting surveillance authorities could harm them in the immediate aftermath of a terrorist attack.

One official pointed to the New Year’s attack on an Istanbul nightclub, which killed 39 people and injured at least 70 others, including a businessman from Delaware who was shot in the leg.

Using information collected at the scene, one senior U.S. official said trackers “were able to identify information about his potential location,” passing the information along to Turkish law enforcement, who arrested the attacker.

Some leads for electronic surveillance come from “pocket litter,” or the phone numbers and email addresses found on terror suspects who fall into the hands of authorities, officials said.

Authorities also spoke of a foreign cyber operation targeting the United States that was broken up using surveillance, but didn’t identify the nation from which the perpetrators operated or offer further details. They declined to say if the nation was Russia.

Intelligence officials said they worry that Congress may impose restrictions designed to keep U.S. citizens or permanent residents out of electronic dragnets that will inadvertently harm other aspects of surveillance.

Addressing the issue of how many U.S. persons are snared, authorities recently briefed oversight committees in a closed session to explain that any estimate is “an unknowable fact.”

Often times, one official said, “We simply don’t know the identity or nationality or location of a subject.” He added that email addresses do not reveal nationality.

Criticism of the surveillance programs has come from the ultra-conservative Freedom Caucus, which said June 15 that surveillance has “violated Americans’ constitutionally protected rights,” demanding substantial reforms if Section 702 is to be reauthorized.

President Trump has grumbled on Twitter about “the ‘unmasking and surveillance’ of people that took place during the Obama administration,” but has not personally spoken about the re-authorization of the Section 702 powers.

Some Democrats have complained about what they say is constitutional overreach in the collection, believing that millions of communications of Americans are vacuumed up and kept for up to five years in data repositories.

“Rational people can certainly disagree on whether our protections are sufficient,” said a senior NSA analyst, who cannot be further identified under rules set by the agency.

The Justice Department and FBI do not have any information supporting President Trump's tweets alleging that President Obama ordered him to be wiretapped, said FBI Director James Comey during testimony before the House Intelligence Committee on Mo McClatchyC-SPAN